Wide band coupling system



3 Shasta-Sheet 1 OLD A. WHEELER INVENTOR e v '2 Frequency FIGS.

ATTORNEY July 25, 1939. H. A. WHEELER WIDE BAND COUPLING SYSTEM FiledApril 22, 1938 FIG.|O.

E. L C

July 25, 1939. H. A. WHEELER WIDE am: courune sys'rau Filed April 22,1938 3 Sheets-Sheet 2 INVENTOR you: A. WHEELER 8 ATTORNEY July 25, 1939.H. A. WHEELER WIDE BAND COUPLING SYSTEM Filed April 22, 1938 3Shasta-Sheet 3 INVENT HARO LO A. WHEELER U 54 m ATTORNEY Patented July25, 1939 a um'rso sr rs s., PAT'sNT 1 OFFICE 1 am-1a,; wins B ND courrmosrsrau Harold a. wheeler-{amt Neck. N. 1.. assignmto Haseltine corporation. a corporation oi Del- 1 Application awn a, ma. Serial N0. 20am140mm (cine-+41 This invention relates generally-to wide band couplingand particularly to such coupling systems including one or more pairs ofterminals, in series with one or more pairs of which there iseflectively included substantial inductance and between the said one ormore pairs of which it is desired to'build. up a high admittance whichis substantially constant over a wide range of frequencies. v

In many coupling systems it is desirable to build up between a pair ofterminals thereof a substantially uniform admittance having the largestpossible mean value over a wide range of frequencies. For example, inthedesign of a coupling system for coupling a generator having appreciableseries inductance to a current-responsive load; it is desirable to buildup through the inductance of the circuits to be coupled the maximumadmittance whichcan be maintained substantially uniform over theoperating frequency range of the system. Prior art coupling arrangementsdesigned for this purpose have fallen far shortof the desired results.It is an object or the present invention, there'- fore, to provide awide band coupling system comprising one or more pairs of terminals,atleast one pairhaving associated therewith substantial seriesinductance and between. which a maximum mean value of admittance ismaintained over a wide frequency range. i

It isanother object of the invention to provide a coupling system havingmaximum transfer admittance over a wide frequency range for use betweena voltage-regulated generator and any kind of a load circuit, or betweenany kind are generator and a current-responsive load. 1

In accordance with the lnvention,'.a signaltranslating system foroperation overa wide range oi frequencies comprises one or more pairs ofterminals in series,- with one pair .of which there is substantialreactance tending to limit the response of the system over its 'range. Adeadend filter'is provided having a predetermined image impedance overthe range coupiedto the one of the pairs of terminals, theiilter'comprislngonlya part of the reactance the said pair of terminalsas a terminal midseries element and having an impedance terminationcoupled to the dead end tioned substantially to match the imageimpedance of the filter over the range; The reactive constants of thedead-end filter'are, so proportioned relative to the reactanoeassociated with the said pair of terminals and the operating fre quencyrange that the mean value of the admitfl r ciated with oi' the filterpronorthe of the filter tance between the said pair of terminals overthe range is substantially the maximum value that can be'maintainedtherebetween over the range. Other modifications of the dead-end filterof the inven io are described and claimed in'applicant's copendingapplications SeriaiNo. 203,595, serial No. 203,597, and Serial No.203,598, filed concur-" rentlyl with the present application while a general circuit arrangement for maintaining unlform impedance over the widerange or frequencies across a pair of terminals having assoelatedtherewith inherent inductance tending tolimit the response of the systemis described and broadly claimed in applicant's related copendingapplication ,Serial No. 161,017, filed August 26, 1937, all assigned tothe same as'signeeas the present application.

Thenovel features believed to be characteristic of the invention are setforth with particularity.

in the appended claims. The invention itself. howeven both as to itsorganization and method of operation, together with further objects andadvantages thereof, will best be understood by reference to thespecification taken in connection with the accompanying drawings, inwhich Fig. 1

is a: simplified orequivalent circuit diagram ofa j coupling network emodying the invention and is utilized to explain the theory of theinvention: Fig. 2 isia' graph iliustratingcertain of the operatingcharacteristics" of the circuit of Fig. 1:

Figs. 3, 4; and 5 are circuit illustrating difierent 'embodiments'oftwo-terminal networks the invention; Figs. Git-8c, inclusive. arecircuit diagrams utilized to explain ditferent embodiments oftour-terminal networks utilizing the invention; while Figs.911,inclusive, illustrate different embodiments of a tour-terminalnetwork utilizing the invention.

The principles and theoretical relations underlying the invention aredescribed most simply by reference to a non-dissipative wave filter ofthe constant-k type. This filter may be assumed to have an infinitenumberofsections or to be terminated with its image impedance to givethe same effect. Thelnput impedance of such a filter is uniform overitspass bands ii the input termi-J nation is fullseries or. full-shuntas. distinguished from the usual mid-series or mid-shunt termination.The input impedance is the iterative im, pedance measured outside of afull-series or fullshunt arm as distinguished from the conventionalimage impedance considered at mid-serge or mid-shunt. This inputgarded-as a two-terminal coupling. impedance,

servingmerelyasa impedance may ref I lit The uniform full-seriesiterative impedance through inductance L then has a magnitude R'=LAu/2(2) This relationship the theoretical minimum value of impedance, or,reciprocally, the maximum value of admittance, that can be maintainedthrough an inductance L over pass bands of total width An. In the caseof a simple lowpass filter, this minimum value of impedance is half thereactance of inductance L at the cutoff frequency. I

The problem reciprocal to building up the admittance through aninductance is building up the impedance across capacitance. A filter canbe arranged to include directly in series with all the other elements ofits series arm a capacitance of the value C which is equal to in which Ris the mid-band image impedance and A is 2: times the total width of thepass bands. The uniform full-shunt iterative impedance across thecapacitance C has the magnitude This relationship expresses thetheoretically maximum value of admittance that can be maintained acrossa capacitance C of the frequency bands of total width An. In the case ofa simple low-pass filter, this value is half, the capacitance of C atthe cutoff frequency. The specification will not be generalized toinclude derivations of expressions given to maintain a given value ofcapacitance across a condenser because all the relations hereinaftergiven can be applied to this problem by the analogy which appears in thepreceding formulae.

The image impedance of a filter of the type under discussion is purelyresistive in the pass bands, although not uniform. On the other hand,the uniform iterative impedance has a substantial phase angle which is alagging phase angle as referring to the voltage across a capacitance orthe current through an inductance. The phase characteristic is that of ahalf-section of a constant-k filter. A more general analysis is givenherein after with reference to a simple low-pass filter without any lossof generality in the foregoing concepts.

Referring now to the drawings, Fig. 1 shows the basic low-pass filtercircuit in a simplified form, the filter, per se, representedschematically at I, having input terminals 8 and outputterminals 8. Theinput termination Lu of filter 1, is a mid-series element and the inputadmittance Yg' Z where Z1 is the input impedance, follows theconstant-Ic characteristic. The output termination of filter I is eithermid-series or mid-shunt and its image impedance Z1 preferably follows anmderived characteristic to match closely the output load resistance Ro-In developing the theoretical relationships involved, this impedancematchingisassumedtobeexactinthepassband,

aromas since any required degree of approximation is possible by meansof multiple m-derivations.

For the sake of clarity and generality, the total inductance I. inseries with the input terminals 8 may have any value and is, fortheoretical purposes, divided into two parts, In comprising themid-series inductance termination of the filter and In, the externaladded inductance. thus, only a part of the total inductancein serieswith the terminals I is includedjn the filter as.a mid-series element.The input admittance Yi is, therefore, in series with the totalinductance Lo=Lm+La- This admittanceis to be built up with the aid of adead-end filter acting merely'as a passive auxiliary network.

The series inductance 1m in the filter is a mid series element of aterminal half-section. This half-section may be oi. the m-derived type(1n 1) or a constant-k type (m=1) since either type is available in aform whose mid-series termination presents the desired constant-k imageadmittance Yi in series with the input terminals 1. In such ahalf-section the value of the mid-series inductance is I in which as isBelt, where I. is the cutoff frequency of the low-pass filter. Theexternal series inductance In can have any value as determined by thechoice of the parameter a in the formula nR, il-1 (5) Therefore, thetotal series inductance is I Lo=Im+Ln=(m+n)Ra/uc (5) The factor (m+n)may have any positive value. One of the parts may be negative, since theparts do not have to exist separately. Negative In merely means that thetotal inductance Lo is less than the mid-series inductance In of thefilter. Equation 5 may also be written as The image impedance Z: dependsonly on R0 and we, not on In and m, because it always has the constant-kcharacteristic Z.-I -+.i -I l +1 This expression has a discontinuity atthe cutoff frequency (:l:=1) where the Z: term of the denominatorchanges from real to imaginary. It is seen that the form of theadmittance characteristic depends only on fl=lnwclRo (11) from Equation4 and does not depend on m=L1wc/Ro (12) from Equation 8.

magnitude is li icl 7- 7-711 xiv- 1)" In the par band (Ki), m is complexand its values of n, it has a value of that of a simple resistance andinductance in series, although the phase angle is not the same. Theadmittance has alag'ging phaseangle is the same as the expression foradmittance phase angle of a half-section iii-derived filter except thatthe m of the filter is replacedby the parameter n which determinestherelative value of If n=1; Equation 14 simpliflesto 1 =sina:' (is) Inthe attenuation band (a: 1), YR is imaginary and its magnitude is It hasa lagging phase angle b=rl2. 'l hese characteristics cannot be realizedexactly, becausethe output image impedance 2; cannot match R outside thepass band. As the attenuation increases, this failure has less effect onthe input admittance. Therefore, any degree of approximation the inputside so that m='i, the values-+1 and --1 for 1: correspond, respectivelyto full-series and full-shunt termination. In the former case, theaddition of 1m doubles the mid-series element, while in the latter caseit cancels the mid-series element.v Theslgn of the-parameter a does notailect the magnitude tor the admittance in the band, but itdoesd'etermine the signal the phase angle. i 5 7 Since-only positiveself-reactance elements can a p he realized in a passive'network thevalue of m in 5 theendjhalf-section'of a filter must be between zero and+1. Since m+nmust be positive, the

' P value of u must be between 1-,-1 and +w, Negative values of nniakethe admittance infinite at the f u nc 4 I: I; (17) I 1jn Athigher-frequencies, the phase angle is reversed in sign, b=1r/2.

Forgiven values ofa'dmittance and band width,

any of the admittance characteristics of Fig. Zare theoreticallyobtainable in-series with the maximum possible value of totallnductanceii' a circult is chosen which has m=1, 11 having the valueidentified with the characteristic curve. If m is less than one, thetotal inductance tolerable directly inlseries with the input terminalsis less by the amount'added indirectly in series with the inputterminals through the other. arms of thefilter. Therefore, a uniformadmittance equal to I/Ro in the pass band is obtainable across amaximumtotal inductance directly and indirectly in series; whose valueis computed byletting ni =n= the ""0 if n =1, YR, is constant" (unity);for greatera this tolerance increases with n. The number of sections inthe filter affects the number-of peaks and valleys in the actualimpedance curve of Y1, while the phase characteristicsafiecttheirspacing along the frequency I j The general concepts utilized above todevelop the expressions relating to low-pass filters are generally valid'for filters having any number of pass bands. The mid-series inductance1m may be supplemented by series elements to form an impedance networkof the form require'd in.a constant-k series arm to give the requiredpass bands. In also may be likewise supplemented. so that the inside andoutside series arms can still be merged into one. The generalizedrelation corresponding to Equation 8 is Lomwllia=in+11 (19) in which Ais thetotal width of all pass bands. Uniform admittance of magnitude1/3. is secured in all the pass bands if n=l. It'is secured with maximumseries inductance if also 1n=1. The expression LoAM/Ro, for anycondition of uniform admittance may be designated as a1"figureof merit",its maximum value being two.

Figs. 3 and 4 illustrate different embodiments o'f two-terminal low-passcoupling networks utilizing the dead-end filter of the invention. Fig. 3comprises. in the order named, the external inductance Ln inserles withwhich a generator supplies a voltage of a value E1. resultingin acurrent of avalue 1|. The dead-end. fllterof the invention comprises, inthe order named, an m-derived halisection, indicated as m, of whichinductancelm is a mid-series element, and a terminating resistor R0, theresistance of which matches-the image. impedance. of the dead end ofthefilter exactly atftwo points in the passband and very closely overmost of the-band, "The network of li'ig. 4

comprises an external inductance ,Lswhiohma'y be the internalinductance, of a generator and in serieskwithwhich is applied a voltageE1 resulting named. an m-derived half-section indicated as m in-thedrawings'of which inductance I... is a midseries element, a doublem-derived section indicated as mm; and a terminating resistorRortheresistance of which matches the image impedance ofthe dead end of thefilter exactly at three points in the pass band.

In Fig. 5 there is shown a two-terminal bandpass coupling networkutilizing the, invention. Thisnetwork comprises a series-resonantcircuit including inductance 1m and capacitance Ca in serieswith whichis supplied a voltage E1, resulting in a current I: in the system. Osmaybe an element of the circuitwhich may be comprised .in the inherentcapacitance of the system andtends to limit the 'response,or it maybe anadditional added element and is necessaryto convert the filter to aband-passfilter. The dead-end filter of the invention comprises. in theorder named, an rn-derived haifssection of which the series-connectedinductance 1- andcapacitancecscomprise amidseriesamandaterminatingresistorltotheredistance oiwhichmatches theimage impedance of the dead-end filter exactly at four points in thepamband. ThecircuitsoirigaiandtabovearemorecompIexthanthatoII'lgJandAuetothe added elements, provide a morenearly constant response over the pass band.

The low-pass examples of two-terminal networks described above may beutilised to maintain maximum admittance through an inductance element.for example. to secure maximum current from a voltage-regulatedgenerator, such as a moving coil having small internal resistance andappreciable inductance. The inductance may be the total 01 that of boththe input and output circuits of the system.

The dead-end filter oi the invention also may be utilized in afour-terminal network and the other of the two two-terminal devices. thegenerator and the load, may have either shunt capacitance or seriesinductance. The signal transfer is then limited by the series inductanceone device and either series inductance or shunt capacitance of theother. There are several permutations 0! such four-terminal networks. Ingeneral. each of the terminal devices is limited in performance over awide frequency band by either shunt susceptance or series reactance. Acurrent-regulated generator or voltage-responsive device have in commonthe property of small shunt inductance and the limitation is imposed byshunt capacitance. ,A voltage-regulated generator or acurrent-responsive load have in common the property of small seriesresistance and the limitation is imposed by series reactance. Thetour-terminal networks of the invention employ the principles utilizedabove for maintaining uniform admittance through series reactance, overa wide band of frequencies. and employ similar principles. described indetail in the abovementioned application Serial No. 203,295 to maintainuniform impedance across susceptance. The total capacitance andinductance oi the circuits to be coupled may be divided into thesmallest possible component portions and included in difierent sectionsof a. filter, so that the impedance oradmittance oi the filter islimited, not by the total, but by the greatest indivisible portion.

The tour-terminal networks of the invention may be analyzed byseparating the input and output devices in the filter instead ofconnecting them directly in series or in parallel. Further benefits maybe obtained by further subdivision involving more than two pairs ofterminals, the other pairs being within the two essential parts 01 thefilter. For example. the capacitance to ground of connecting leads or oia large grid condenser may be separated from other circuit reacta'ncesand may comprise a reactance element of another section of the filter.

Figs. 60-80, inclusive, are the bases of the theoretical analysis offour-terminal networks. They are developed from low-pass filters butexemplify all filters having a finite total band width. The capacitiveand inductive arms shown are, respectively. parallel and series arms oflowpass filters. Figs. def-6c. inclusive. represent the development ofthe filter for building up uniform admittance through series inductance.Fig. 6a is essentially a two-terminal network with the total inductanceIn of elements Ian and La in s'eries with its terminals. In Fig. 6a. therelationship oi Equations 3, 4, and 5 given above apply. The dead-endfilter of Fig. 6a is assumed to aid-mes be non-dissipative. It is showndivided into two parts it and Ii, which divisionisabasisiorthe analysisof the tour-terminal networks. The dead-end filter II. I I correspondsto filter I shown inl'ig. iandsimilarelementshavebeengiven identicalreference numerals. Elements 10' and 1-" are. respectively, themid-series inductances of parts I. and II at their adiacent ends. Thenetwork it is supplied with an input voltage E1 irom a voltage-regulatedgenerator which supplies through the filter the output current I: whichis the same as the input current I1 supplied through if irorn thegenerator:

The part ll of the dead-end filter is "symmetrical"in that it has theconstant-k mid-series image impedance at both ends. This does notrequire symmetry oi circuit arrangement within the filter and does notrequire any constant-k halisections within the filter, although bothoi'- these attributes may be present. The part ii 0! the dead-endfilterhas a constant-k mid-series image impedance at its end coupled to partIt, while at the opposite end it prei'erably has an m-derived imageimpedance assumed to match the terminal resistance Ra over the passband. At the Junction or parts II, N the mid-series inductance elementshave the values:

L-l mIR/w; L!I m!!Ra/0c Ld'=L-'+L-"=(m'+m"lR/u' in which at and 1n" arethe derivation i'actors or the two parts of the filter. In is the totalinductance at the junction. usually a single circuit element.

Since the part it of the dead-end filter is nondissipative and has thesame image impedance at both ends and since the entire filter isterminated by R0 in such a manner as to prevent refiection. there isdeveloped at the junction of parts Ill and ii a current equal to thatsupplied to the input terminals. although displaced in phase. Therefore,the output current can just as well be obtained at the junction as shownin Fig. 6b. It is then determined by the characteristics of both theinput admittance Y and transfer admittance oi part II oi the filter:

I; I I; E==El-i;=Y (TO'-fl) (22) in which (c-Hb) represents theattenuation in napiers, and the phase lag in radians in part In of thefilter. Part 11 is still inactive and functions only as a dead-endnetwork to control the impedance. The attenuation a is assumed to bezero in the pass band.

The phase shift and attenuation obtained by making the part ll of thefilter active between input and output terminals may or may not bedesired. but there is a definite advantage in work. Therefore, thenetwork oi Fig. 6b can be reversed as shown in Fig. 6c, while retainingits transfer characteristics unchanged. The dead end of the filter ischanged from the output side to the input side.

Figs. 7040, inclusive, show the development of coupling networks inwhich the input and output circuits have reciprocal properties, that is,shunt susceptance and series reactance. or vice versa. The active partof each filter has "reciprocal symmetry of image characteristics; thatis, it has mid-shunt image impedance at one end and mid-series imageadmittance at the other, both being of the constant-k form. Since theyare reciprocal, the quotient of output current and input voltage, or ofoutput voltage and input current, is constant in the pass band, althoughsubject to phase shift. The constant value of the quotient is themid-band image impedance R or its reciprocal Go- These relationshipsfollow from the conservation of power as the waves travel through thefilter. In Fig. 7, the essential property of the four-terminal networkis its transfer ratio,

The same transfer ratio is retained in Fig. 7c in which the order ofcomponents is reversed:

.l E1 E1 E1 Zo q-n In Fig. 8b, the essential property of the filter isits transfer ratio,

In any of the low-pass filter examples, the susceptance may be the shuntcapacitance of a current-regulated generator or a voltage-responsiveload, while the inductance is the series inductance of avoltage-regulated generator of a current-responsive load.

Each of Figs. 9 and 10 shows a practical arrangement embodying the aboveprinciples in a low-pass four-terminal network. The terminal circuitsare indicated in the drawings by E1 or In and E2 or I2. Thus, Fig. 9shows a four-terminal network comprising, in the following order, anexternal inductance Ln, 9. constant-k section indicated as k in thedrawings comprising inductance In as a mid-series element thereof, aconstant-k half-section also indicated as k in the drawings, anm-derived section indicated as m' in the drawings, and a terminatingresistor R which matches the image impedance of the dead end of thefilter over the pass band. It will be seen that the circuit of Fig. 9may thus comprise a generator having appreciable inherent inductance(Ln+Lm) and in inductive load (the inductance of which may be as largeas the inductances of the filter circuit of Fig. 9 which are in serieswith the load current 12). The inductance of the load and that of thegenerator are separated by shunt susceptance.

The filter of Fig. 10 comprises, in the following order, the externalcapacitance Cn, a. constant-k half-section of which capacitance Cm isthe mid-shunt element, an m-derived half-section indicated as m", and aterminating resistor R0 which matches the image impedance of the deadend of the filter over the pass band. The circu t 9 F 5. 19 y be ii zeto co ple a capacitive generator (the capacitance of which isrepresented by Cs and Cu) to an inductance load (the inductance of whichis-represented by the inductors'in series with the load circuit Ia) Theband-pass filter of Fig. 11 comprises, in the following order.series-connected external elements On In, a constant-k half-section ofwhich C. and Lin comprise the mid-series arm, an m-derived half-sectionindicated as m', and a terminating resistor R which matches the imageimpedance of the dead end of the filter over the pass band.

As illustrative of the practical applications of the above-describednetworks, the following list includes various types of wide bandnetworks and some of the uses to which they are adapted.

The dead-end filter of the invention may be on the input or the outputside. In this list shunt capacitance is denoted by (C); seriesinductance is denoted by (L); and the combination of both in series orparallel is denoted as (CL). Each of these elements may be included inthe filter design.

Tmvrsron Video-signal translator (band-pass) Amplifier anode (C) toshielded line to lowimpedance antenna (CL), the limiting factor beingseries reactance.

Low-impedance antenna (CL), the limiting factor being series reactance.to shielded line to amplifier grid (C).

Scanning (low-pass) Amplifier anode (c) to deflecting coils (CL), thelimiting factor being series reactance.

Scanning (band-pass) Amplifier anode (C) to transformer (CL) todeflecting coils (CL), the limiting factor being series reactance.

Audio frequency (band-pass) Moving coil (L) microphone or phonographpick-up to transformer (CL) to amplifier grid (C).

Amplifier anode (C) to transformer (CL) to moving coll (L) loud-speakeror receiver.

Condenser (C) microphone or phonograph pick-up to transformer (CL) toamplifier grid (C).

Amplifier anode (C) to transformer (CL) to condenser (C) loud-speaker orreceiver, the limiting factor being series reactance.

The low-pass networks here shown are, as mentioned above, illustrativealso of networks generally having pass bands of finite total band width.The four-terminal devices are illustrative of networks having any numberof. input circuits or of output circuits, each with a pair of terminals,disposed along the filter in the manner of the second device insertedbetween the active and inactive parts of the dead-end filter in Figs.Geo-8e, inclusive.

In the design of the dead-end filters of the invention the preferredvalue of m in the mderived sections is of the order of 0.6. Values of mbetween the limits of 0.5 to 0.7 result in a matching of the imageimpedance of the mclerived filter section with the terminating resistorRn at two points in a low-pass band, or four points in a band-passfilter. Filters having an m-derived termination with a value of mgreater than 0.7 cannot match the terminal resistor R0 at more than onepoint in a low-pass band, or two points in a band-pass filter. Eachadditional m-derivation included in the filter termination makes itpossible to match the image impedance with the terminal resistor at oneadditional point in a low-pass band, or two additional points in aband-pass filter.

While there have been described what are at present considered to be thepreferred embodiments of this invention, it will be obvious to thoseskilled in the art that various changes and modifications may be madetherein without departing from the invention. and it is, therefore.aimed in the appended claims to cover all such changes and modificationsas fall within the true spirit and scope of the invention.

What is claimed is: a

i. A signal-translating system for operation over a wide range offrequencies comprising one or more pairs of terminals in series with onepair of which there is substantial reactance tending to limit theresponse of said system over said range, a dead-end filter having apredetermined image impedance over said range coupled to said one ofsaid pairs of terminals. said filter comprising only a part of said rea;tance as a terminal mid-series element of said filter and an impedancetermination coupled to the dead end of said filter proportionedsubstantially to match the image impedance of said filter over saidrange, the reactive constants of said dead-end filter being soproportioned relative to said reactance and the operating frequencyrange that the mean value of, the admittance between said one pair ofterminals over said range is substantially the maximum value that can bemaintained therebetween over said range.

2. A signal-translating system for operation over a wide range offrequencies comprising one or more pairs of terminals in series with onepair of which there is effectively inductance tending to limit theresponse of said system over said range, a dead-end filter having apredetermined image impedance over said range coupled to said one ofsaid pairs of terminals, said filter comprising only a part of saidinductance as a terminal mid-series element of said filter, and animpedance termination coupled to the dead end of said filterproportioned substantially to match the image impedance of said filterover said range, the reactive constants of said dead-end filter being soproportioned relative to said inductance and the operating frequencyrange that the mean value of the admittance between said one pair ofterminals over said range is substantially the maximum that can bemaintained therebetween over said range.

3. A signal-translating system for operation over a wide range offrequencies comprising one or more pairs of terminals in series with onepair of which there is effectively capacitance tending to limit theresponse of said system over said range, a dead-end filter having apredetermined image impedance over said range coupled to said one ofsaid pairs of terminals, said filter comprising only a part of saidcapacitance as a terminal mid-series element of said filter, and animpedance termination coupled to the dead end of said filterproportioned substantially to match the image impedance of said filterover said range, the reactive constants of said dead-end filter being soproportioned relative to said capacitance and the operating frequencyrange that the mean value of the admittance between said one pair ofterminals over said range is substantially the maximum that can bemaintained therebetween over said range.

4. A signal-translating system for operation over a wide range offrequencies comprising two pairs of terminals, each pair of which has inseries therebetween substantial reactance tending .to limit the responseof said system over said range, a dead-end filter having a predeterminedimage impedance over said range coupled to one of said two pairs ofterminals, said filter comprising only a part of the reactance in serieswith said one of said two pairs of terminals as a mid-series terminalelement of said filter and comprising the reactance in series with theother of said two pairs of terminals as a full-series intermediateelement'of said filter, and an impedance termination coupled to the deadend of said filter proportioned substantially to match the imageimpedance of said filter over said range. the reactive constants of saiddead-end filter being so proportioned relative to said reactances andthe operating frequency range that the mean value of admittance betweensaid one of said two pairs of terminals over said range is approximatelythe maximum that can be maintained therebetween over said range.

5. A signal-translating system for operation over a wide range offrequencies comprising two pairs of terminals, in series with each pairof which there is substantial inductance tending to limit the responseof said system over said range, a dead-end filter having a predeterminedimage impedance over said range coupled to one of said two pairs ofterminals, said filter comprising only a part of the inductance inseries with said one of said two pairs of terminals as a midseriesterminal element of said filter and comprising the inductance ln serieswith the other of said two pairs of terminals as a full-seriesintermediate element of said filter, and an impedance terminationcoupled tothe dead end of said filter proportioned substantially tomatch the image impedance of said filter over said range, the reactiveconstants of said dead-end filter being so proportioned relative to saidinductance and said operating frequency range that the mean value ofadmittance between said one of said two pairs of terminals over saidrange is approximately the maximum that can be maintained therebetweenover said range.

6. A signal-translating system for operation over a wide range offrequencies comprising two pairs of terminals, across one pair of whichthere is effectively a substantial capacitance and in series withanother pair of which there is effectively a substantial inductance,said inductance and said capacitance tending to limit the response ofsaid system over said range, a dead-end filter having a predeterminedimage impedance over said range coupled to one of said pairs ofterminals and comprising only a part of the capacitance associated withsaid one of said pairs of terminals as a terminal mid-element of saidfilter and comprising the inductance associated with the other of saidtwo pairs of terminals as a full element of said filter, and animpedance terminaan coupled to the dead end of said filter proportionedsubstantially to match the image impedance of said filter over saidrange, the reactive constants of said dead-end filter being soproportioned relative to said capacitance and inaromas value that can bemaintained over said range.

' '1. a; signal-translating mm for operation over a vwide range oifrequencies comprising two 'pairsotterminalsinserieswitheachpairoi minedimage impedance over said range coupled to one oi. said pairs terminalsand comprising only a part 01' the inductance in series therewith as aterminal mid-series element oi said filterand comprising the inductancein series with the other of said pairs of terminals as a full-serieselement oi' said filter, and an impedance termination tor the dead endof said filter proportioned substantially to match the image impedanceoi said filter over said range, the reactive constants oisaid dead-endfilter being so propotioned with respect to said inductances and saidoperating range that the mean value of admittance between said one oisaid pairs of terminals is substantially the maximum that can bemaintained between said one oi said pairs of terminals over said range.i

8. A signal translating system for operation over a wide range oftrequencieslncluding a generatorhaving appreciable inductanceand aninductive load coupled to said generator, the inductance oi said.generator and said load tending to limit the response oi said systemover said range, a dead-end filter having a predetermined imageimpedance oversaid range coupled to said generator and said load, saidfilter comprising-only a part of said inductances as a terminalmidseries element, and an impedance termination coupled to the dead endof said filter proportioned substantially to match the image impedanceof said filter oversaid range, the reactive constants of said dead-endfilter being so proportioned relative to said inductances and theoperating frequency range that the meanvalue 0! transferadmittancebetween said generator and said lead is substantially themaximum that can be main-1 tained over said range.

A low-pass signal-translating system for op,- -eration over a wide rangeof frequencies including a generator having appreciable inductance andan inductive load'coupled to said generator,

the inductance of said generator and said lead tending to limit theresponse of said system over said range, a dead-end filter having apredetermined image impedance over said range coupled to said generatorand said load, said filter comprising only a part of said inductances as.a terminal mid-series element, a double m-derived impedance terminationat the dead end oi said illter, and a terminating resistor coupled tosaid mderived termination, said m-derived termination being proportionedsubstantially to match the image impedance of said filter with saidresistor over said range and exactly to match the image impedance ofsaid filter with said resistor at three ,points in said range, thereactive constants of said dead-end filter being so proportionedrelative to said inductances and the operating irequency range that themean value 01' transfer admittance between said generator and said loadis substantially the maximum that can be maintained over said range.

10. A low-pass signal-translating system for operation over a wide rangeor frequencies including a generator having appreciable inductance andan inductive load coupled to said generator, the inductance of saidgenerator and said 7 load tending to limit the response of said systemover said range, a dead-end filter having a pre-,

tion being proportioned substantially to match the image impedance ofsaid filter with said resistor over. said range and exactly to match theimage impedance oi said filter with said resistor at two points id saidrange, the reactive constants 01' said dead-end filter being soproportioned relative to said inductances and the operating frequencyrange that the mean value of the transier admittance between saidgenerator and said load is substantially the maximum that can bemaintained over said range.

11.- A band-pass signal-translating system for Operation over a widerange of frequencies including a generator having appreciable inductanceand an inductive load coupled to said generator, the inductance of saidgenerator and said load tending to limit the response oi said systemover said range, a dead-end filter having a predetermined imageimpedance over said range coupled to. said generator and said load, saidfilter comprising only a part of said inductances as a terminalmid-series element, an impedance termination for said filter comprisingone tuned circult in a series arm and a pair 01 tuned circuits in ashunt arm, and a terminating resistor for said impedance termination,said impedance termination being proportioned substantially to match theimage impedance 01 said filter with said resistor over said range andexactly to match the image impedance of said filter with said resistorat four points in said range, the reactive con- I stants of saiddead-end filter being so proportioned relative to said inductances andthe opertransfer admittance between said generator and said load issubstantially the maximum that can be maintained over said range.

12. A signal-translating system for operation over a wide range offrequencies including a generator having appreciable inductance and aninductive load coupled to said generator, the inductances of saidgenerator and said load being separated by shunt capacitance whichtogether tend to limit the response of said system over said range, adead-end filter having a predetermined image impedance over said rangecoupled to said generator and said load, said filter comprising only apart of one of said inductances as a terminal mid-series element andsaid capacitance as I a full-shunt element, an impedance terminationcoupled to the dead end oi. said filter proportioned substantially tomatch the image impedance of said filter over said range, the reactiveconstants of said dead-end filter being so proportioned relative to saidone of said inductances, said capacitance, and the operating frequency.over a wide-range of frequencies including a capacitive generatorcoupled to an inductive load, the capacitance oi! said generator and theinductance oilsaid load tending to limit the respouse of said systemover said range, a deadend filter having a predetermined image impedanceover said range coupled to said generatorandsaidloadsaidfiltercomprisingonlrapart of said capacitance as aterminal mid-shunt element and said inductance as a full-series element,an m-derlved impedance termination comprising a series-resonant shuntarm coupled to the dead end of said filter. and a resistor coupled tosaid impedance termination. said impedance termination beingproportioned substantialiy to match the image impedance oi said iilterover said range, the reactive constants 01 said dead-end filter being soproportioned relative to said inductance and said capacitance and theoperating frequency range that the impedance across said generator issubstantially uniiorm and substantially the maximum that can bemaintained thereacross over said range.

14. A signal-translating system for operation over a wide range oifrequencies including a generator having appreciable inductance and acapacitive load coupled to said generator. the inductan'ce of saidgenerator and the capacitance oisaidlosdtendingto limit theresponseoisaid system over said range, a dead-end filter having apredetermined image impedance over said range coupled to said generatorand said lead. said filter comprising only a part or said inductance asa terminal mid-series element and said capacitance as a full-shuntelement, an mderived impedance termination comprising a series-resonantcircuit and a parallel-resonant circuit coupled in parallel as a seriesarm, a terminating resistor coupled to said impedance termination, saidimpedance termination being proportioned substantially to match theimage impedance of said filter with said resistor over said range. thereactive constants of said dead-end filter being so proportionedrelative to said inductance and the operating frequency range that themean value of admittance between the terminals oi said generator issubstantially the maximum 20 that can be maintained over said mustCertificate oi! Correction Patent No. 2,107,135.

numbered atent req correction asfollows: strike out quation 5, and

out Equation 6,

July 25, 1939.

in the printed specification of the above age 2, second column, line 36,

msert instead L,=L,,,+L,,;=(m+n)R ,/w,; line 44, strike and insertinstead w,,= (m-i-n)R,;/L,; hne 4:5 strike out Equation 7,

and insert instead R,=L.,w,/ (gn+n) line 47, strike out E uation 8, andinsert instead strike out line 58, and

meter z==wlw,; hne nation 11, and insert instead m- -L,,w,,/R,,; secondcolumn, bus 29, st strike out line 34, and msert instead ezpr gangs 5,first column, line 62, for

insert instead i "admittance insert of; hue 70, strike out insertinstead n=L,,u,,/R,,;

age 3, first column, e out Equation ess'ion L,,Aw/R,,, for an in readan; and that the ear is convenient to use the line 74, strike outEquation 12, and line 5, for YR, read }YR,1; and and insert insteadL,,Aco R,,'=m+n;

condition of an arm; Letters Patent s ould read with these correctionstherein that the same may conform to the record of the ease in thePatent Ofiice.

Signed and sealed this 24th day of October,

HENRY VAN ARSDALE,

end filter having a predetermined image impedance over said rangecoupled to said generator andsaidloadsaidfiltercomprisingonlrapart ofsaid capacitance as a terminal mid-shunt element and said inductance asa full-series element. an m-derlved impedance termination comprising aseries-resonant shunt arm coupled to the dead end of said filter. and aresistor coupled to said impedance termination. said impedancetermination being proportioned substantialiy to match the imageimpedance oi said iilter over said range, the reactive constants 01 saiddead-end filter being so proportioned relative to said inductance andsaid capacitance and the operating frequency range that the impedanceacross said generator is substantially uniiorm and substantially themaximum that can be maintained thereacross over said range.

14. A signal-translating system for operation over a wide range oifrequencies including a generator having appreciable inductance and acapacitive load coupled to said generator, the inductan'ce of saidgenerator and the capacitance oisaidlosdtendingto limit theresponseoisaid system over said range, a dead-end filter having apredetermined image impedance over said range coupled to said generatorand said lead. said filter comprising only a part or said inductance asa terminal mid-series element and said capacitance as a full-shuntelement, an mderived impedance termination comprising a series-resonantcircuit and a parallel-resonant circuit coupled in parallel as a seriesarm, a terminating resistor coupled to said impedance termination, saidimpedance termination being proportioned substantially to match theimage impedance of said filter with said resistor over said range. thereactive constants of said dead-end filter being so proportionedrelative to said inductance and the operating frequency range that themean value of admittance between the terminals oi said generator issubstantially the maximum 20 that can be maintained over said mustCertificate oi! Correction HAROLD A. WHEELER It is hereby certified thaterrors appear 'on as. follows:

atent re correcti quation 5, and insert instead L,,=L,,,+L,,:=(m+n)R,/w,; line 44, strike and insert instead w,,= (m-i-n)R,;/L,; bus 45,strike out Equation 7,

numbered strike out out Equation 6,

July 25, 1939.

in the printed specification of the above age 2, second column, line 36,

and insert instead R,=L,w,/( m+n);1ine 47, strike out E uation 8, andinsert instead strike out line 58, and

meter z==wlw,; hne nation 11, and insert instead m- -L,,w,/R,,; secondcolumn, bus 29, st strike out line 34, and msert instead ezpr gangs 5,first column, line 62, for

insert instead i "admittance insert of; bus 70, strike out insertinstead n=L,,u,,/R,,;

age 3, first column, e out Equation ession L,,Aw/R,, for an in read an;and that the ear is convenient to use the line 74, strike out Equation12, and line 5, for YR, read }YR,1; and and insert instead L,,AcoR,'=m+n;

condition of an arm; Letters Patent s ould read with these correctionstherein that the same may conform to the record of the ease in thePatent Ofiice.

Signed and sealed this 24th day of October,

HENRY VAN ARSDALE,

